This is code for my DIY ATmega328p based environment monitor project. In EasyEDA - schema folder, there is schematics for this project. It is tested but it can have some flaws. This source code use following libraries:
SparkFun_CCS811 https://github.com/sparkfun/SparkFun_CCS811_Arduino_Library
Adafruit_BMP280 https://github.com/adafruit/Adafruit_BMP280_Library
Adafruit_Si7021 https://github.com/adafruit/Adafruit_Si7021
SSD1306Ascii https://github.com/greiman/SSD1306Ascii